The invention relates to the mounting of electronic devices such as transponders and antennas in pneumatic tires, and to the coupling of transponders to antennas in pneumatic tires.
Examples of the strides Goodyear has taken in the advancement of tire and related technologies includes, but is not limited to, the following patented inventions:
Commonly-owned U.S. Pat. No. 3,665,387 (Enabnit; 1972), entitled SIGNALLING SYSTEM FOR LOW TIRE CONDITION ON A VEHICLE, incorporated in its entirety by reference herein, discloses a low tire pressure warning system adaptable for any number of wheels of a vehicle and providing dashboard indications of system operation and low pressure conditions while the vehicle is in motion.
Commonly-owned U.S. Pat. No. 3,831,161 (Enabnit; 1974), entitled FAIL-SAFE MONITORING APPARATUS, incorporated in its entirety by reference herein, discloses monitoring vehicle tire pressure wherein the operator is warned of an abnormal or unsafe condition of one or more of the tires.
Commonly-owned U.S. Pat. No. 3,872,424 (Enabnit; 1975), entitled APPARATUS AND METHOD FOR TRANSMITTING AUXILIARY SIGNALS ON EXISTING VEHICLE WIRING, incorporated in its entirety by reference herein, discloses communicating with low tire pressure monitoring circuits using power pulses carried on existing vehicle wiring (e.g., the turn signal circuits).
Commonly-owned U.S. Pat. No. 4,052,696 (Enabnit; 1977), entitled TIRE CONDITION MONITOR, incorporated in its entirety by reference herein, discloses a tire condition sensing circuit that includes a ferrite element that changes from a ferromagnetic to a non-ferromagnetic state in response to a temperature increase above the material Curie point.
Commonly-owned U.S. Pat. No. 4,099,157 (Enabnit; 1978), entitled SINGLE WIRE POWER/SIGNAL SYSTEM FOR VEHICLE AUXILIARY DEVICES, incorporated in its entirety by reference herein, discloses providing both power to and receiving detection signals from a remotely located condition monitoring device using a single wire with ground return through the vehicle frame.
Commonly-owned U.S. Pat. No. 4,108,701 (Stanley; 1978), entitled METHOD FOR MAKING HOSE INCORPORATING AN EMBEDDED STATIC GROUND CONDUCTOR, and related U.S. Pat. No. 4,168,198 (Stanley; 1979), entitled APPARATUS FOR MAKING HOSE INCORPORATING AN EMBEDDED STATIC GROUND CONDUCTOR, both incorporated in their entirety by reference herein.
Commonly-owned U.S. Pat. No. 4,911,217 (Dunn, et. al.; 1990), entitled INTEGRATED CIRCUIT TRANSPONDER IN A PNEUMATIC TIRE FOR TIRE IDENTIFICATION, incorporated in its entirety by reference herein, discloses an RF transponder in a pneumatic tire. FIG. 1a of this patent illustrates a prior-art identification system (xe2x80x9creaderxe2x80x9d) that can be used to interrogate and power the transponder within the tire. The identification system includes a portable hand-held module having within it an exciter and associated circuitry for indicating to a user the numerical identification of the tire/transponder in response to an interrogation signal.
Commonly-owned U.S. Pat. No. 5,181,975 (Pollack, et. al.; 1993), entitled INTEGRATED CIRCUIT TRANSPONDER WITH COIL ANTENNA IN A PNEUMATIC TIRE FOR USE IN TIRE IDENTIFICATION, incorporated in its entirety by reference herein, discloses a pneumatic tire having an integrated circuit (IC) transponder and pressure transducer. As described in this patent, in a tire that has already been manufactured, the transponder may be attached to an inner surface of the tire by means of a tire patch or other similar material or device.
Commonly-owned U.S. Pat. No. 5,218,861 (Brown, et al.; 1993), entitled PNEUMATIC TIRE HAVING AN INTEGRATED CIRCUIT TRANSPONDER AND PRESSURE TRANSDUCER, incorporated in its entirety by reference herein, discloses a pneumatic tire having an integrated circuit (IC) transponder and pressure transducer mounted within the pneumatic tire. Upon interrogation (polling) by an external RF signal provided by a xe2x80x9creaderxe2x80x9d, the transponder transmits tire identification and tire pressure data in digitally-coded form. The transponder is xe2x80x9cpassivexe2x80x9d in that it is not self-powered, but rather obtains its operating power from the externally-provided RF signal.
The commonly-owned U.S. Patents referenced immediately hereinabove are indicative of the long-standing, far-reaching and ongoing efforts being made by the Goodyear Tire and Rubber Company in advancing tire product technology.
As used herein, a xe2x80x9ctransponderxe2x80x9d is an electronic apparatus (device) capable of monitoring a condition such as air pressure within a pneumatic tire, and then transmitting that information to an external device. The external device can be either an RF (radio frequency) reader/interrogator or, simply an RF receiver. A simple receiver can be used when the transponder is xe2x80x9cactivexe2x80x9d, and has its own power source. A reader/interrogator would be used when the transponder is xe2x80x9cpassivexe2x80x9d and is powered by an RF signal from the reader/interrogator. In either case, in conjunction with the external device, the transponder forms a component of an overall tire-condition monitoring/warning system. In order to send or receive RF signals, a transponder must have an antenna. This antenna may either be incorporated into the transponder module itself, or it may be external to the transponder module and electrically connected or coupled to it in a suitable manner.
U.S. Pat. No. 5,500,065, incorporated in its entirety by reference herein, and discussed in greater detail hereinbelow illustrates (at FIG. 2 thereof) an exemplary prior art transponder within a tire, and illustrates (at FIG. 5 thereof) an exemplary prior art interrogator which can be used to communicate with and retrieve digitally coded information from the transponder. This patent discloses various methods, described in greater detail hereinbelow, for mounting, including embedding during manufacturing the tire, the transponder (monitoring device) within the tire.
Commonly-owned U.S. Pat. No. 4,911,217, incorporated in its entirety by reference herein, illustrates (at FIG. 1a thereof) another exemplary prior art interrogating tire identification system (10) in combination with a passive integrated circuit transponder (24) in a tire (22).
Safe, efficient and economical operation of a motor vehicle depends, to a significant degree, on maintaining the correct air pressure in all (each) of the tires of the motor vehicle. Failure to correct quickly for faulty/abnormal (typically low) air pressure may result in excessive tire wear, blow-outs, poor gasoline mileage and steering difficulties.
The need to monitor tire pressure when the tire is in use is highlighted in the context of xe2x80x9crun-flatxe2x80x9d (driven deflated) tires, tires which are capable of being used in a completely deflated condition. Such run-flat tires, as disclosed for example in commonly-owned U.S. Pat. No. 5,368,082, incorporated in its entirety by reference herein, may incorporate reinforced sidewalls and mechanisms for securing the tire bead to the rim to enable a driver to maintain control over the vehicle after a catastrophic pressure loss, and are evolving to the point where it is becoming less and less noticeable to the driver that the tire has become deflated. The broad purpose behind using run-flat tires is to enable a driver of a vehicle to continue driving on a deflated pneumatic tire for a limited distance (e.g., 50 miles, or 80 kilometers) prior to getting the tire repaired, rather than stopping on the side of the road to repair the deflated tire. Hence, it is generally desirable to provide a low-pressure warning system within the vehicle to alert (e.g., via a light on the dashboard, or a buzzer) the driver to the loss of air in a pneumatic tire. Such warning systems are known, and do not form part of the present invention, per se.
Numerous tire-pressure warning systems are known in the art. Representative examples of such may be found in the patent references described hereinbelow. The present invention is not limited to a particular type of transponder.
Although the use of pressure transducers in pneumatic tires (in association with electronic circuitry for transmitting pressure data, such as transponder) is generally well known, these pressure-data systems for tires have been plagued by difficulties inherent in the tire environment. Such difficulties include effectively and reliably coupling RF signals into and out of the tire, the rugged use the tire and electronic components are subjected to, as well as the possibility of deleterious effects on the tire from incorporation of the pressure transducer and electronics in a tire/wheel system.
Tires for motor vehicles are either tubeless, or require an inner tube to maintain pressure in the tire. In either case, the tire is typically mounted on a wheel (rim). The use of an inner tube is typical of truck tires, in contrast to tubeless tires which are typically found on cars, pickup trucks, sports/utility vehicles, minivans and the like. The present invention is primarily directed to mounting a transponder within a tubeless tire.
For tubeless tires, various transponder mounting locations are known, and include (i) mounted to an inner surface of the tire, (ii) mounted to the wheel, and (iii) mounted to a valve stem. The present invention is primarily directed to mounting a transponder to an inner surface of the tire.
U.S. Pat. No. 3,787,806 (Church, 1974), incorporated in its entirety by reference herein, discloses a tire pressure warning apparatus for operation in a pneumatic tire in combination with an inner tube. As described in this patent, means are provided to protect the individual components while permitting the necessary flexibility to conform to the shape and motion of the inner surface of the tire. The tire pressure warning apparatus (10) is vulcanized, or otherwise adhered (hermetically sealed) to an external (FIGS. 1-3) or internal (FIGS. 4-6) surface of an inner tube (18). More particularly, the tire pressure warning apparatus (10) comprises a pressure sensor (12), a transmitter (14) and a power supply such as a battery (16). The transmitter (14) is housed in an inflexible enclosure (24) such as a hard plastic box or the like. The battery (16) is housed in a suitable inflexible enclosure (22) such as a hard plastic box or the like. Leads (32, 34) connecting the sensor (12) to the battery enclosure (22) and leads (36, 38) connecting the battery enclosure (22) with the transmitter (14) are formed using stranded wire, and are coiled to permit flexing of the apparatus (10) without incurring wire breakage. The apparatus (10) is encased in any suitable elastic material (40) such as natural rubber or the like, to permit a flexibility comparable to that of the inner tube (18). In the embodiment (FIGS. 4-6) wherein the apparatus (10) is mounted to the inside of the inner tube (18A), the elastic material (40A) is seen to have areas of reduced thickness between the sensor (12A), battery (16A) and transmitter (14A) to readily permit flexing of the warning apparatus (10A). A key feature of the apparatus (10) of this patent is that the pressure sensor (12), transmitter (14) and power supply (16) are separate units connected to one another by flexible leads (32, 34, 36, 38) and surrounded by a flexible material (40) to generate a single composite unit and to permit flexing of each of the separate units relative to one another, the flexible material being adhered to the inner tube and conforming in shape to the inner surface of the tire.
U.S. Pat. No. 5,285,189 (Nowicki, et al.; 1994), incorporated in its entirety by reference herein, discloses an abnormal tire condition warning system comprising a radio transmitting device (A) including a radio circuit (10), a tire condition sensor (20), a control circuit (11) and a battery power supply (12). The radio circuit (10), control circuit (11), sensor (20) and battery (12) are contained in a housing (16) typically of plastic or the like, including a base wall (18) which is configured for close reception against the wheel rim (22) in the tire wheel cavity. Typically, the housing (16) is attached by means of a band (24) and adjustable tightening means (26).
U.S. Pat. No. 4,067,235 (Markland, et al.; 1978), incorporated in its entirety by reference herein, discloses a tire pressure monitoring (measuring) system, and illustrates various embodiments of mounting a remote tire pressure sensor in or on a tire. As shown in FIG. 3, the remote tire pressure sensor (21) may be encapsulated by a suitable elastomeric compound and bonded to the wall of the tire (22). As shown in FIG. 9, the tire pressure sensor (21xe2x80x2) may be formed in the shape of a sphere and introduced inside of the tire as a free-rolling element. As shown in FIG. 8, the tire pressure sensor (21xe2x80x3) may be miniaturized and embedded within the casing of the tire (22) during manufacture. As shown in FIG. 7, the tire pressure sensor (21xe2x80x2xe2x80x3) may be incorporated into a repair plug inserted into the sidewall of the tire (22). Another feature illustrated (see FIGS. 3, 7, 8, 9) in this patent is a receiving antenna 38 and a retransmitting antenna 26, both of which are discussed in greater detail hereinbelow.
U.S. Pat. No. 4,334,215 (Frazier, et al.; 1982), incorporated in its entirety by reference herein, discloses monitoring heat and pressure within a pneumatic tire using a transmitter and other circuit elements mounted to a circuit board which is secured to the inside of the tire by an overlaying elastic adhesive material.
U.S. Pat. No. 5,500,065 (Koch, et al.; 1996), hereinafter referred to as the xe2x80x9c""065 Patent xe2x80x9d, incorporated in its entirety by reference herein, discloses a method for embedding a monitoring device (xe2x80x9ctagxe2x80x9d) within a tire during manufacture. The device can be used for monitoring, storing and telemetering information such as temperature, pressure, tire mileage and/or other operating conditions of a pneumatic tire, along with tire identification information. The monitoring device (10) is comprised of a microchip (20), an antenna (30), an amplifier (42), a battery (44), a pressure sensor (46), and optional temperature and mileage/distance sensors, populating a circuit board (48). The monitoring device may optionally (but desirably) be contained (encased) in a rigid or semi-rigid encasement to enhance rigidity and inhibit straining of the device. The reinforcing encasement or encapsulation is a solid material, i.e., non-foam compounds, which are compatible with the tire rubber, such as various urethanes, epoxies, unsaturated polyesterstyrene resins, and hard rubber compositions. FIG. 1 of the ""065 Patent illustrates a method of securing such a monitoring device (10 or 10xe2x80x2) to an inner wall of a pneumatic tire (5) at two preferred locations: (i) in the vicinity of the tire bead below the end of the body ply turn-up where the sidewall bending stiffness is greatest and where the rolling tire stresses are at a minimum; and (ii) on the inside of the tire at the center of the tread crown where stresses from mounting and dismounting are at a minimum. The specific attachment or adhering means can be through the use of a chemical cure adhesive including a room temperature amine curable adhesive or a heat-activatable cure adhesive. FIGS. 7, 8, 9 and 10 of the ""065 Patent illustrate additional methods of mounting a monitoring device within a tire. An encased monitoring device, or monitoring device assembly (17), can be adhered with a flexible cover (80) while resting on the inner surface of the tire (FIG. 7), or while resting in a pocket formed in the inner surface of the tire (FIG. 8). Suitable housing materials which function to hold the monitoring device to the tire include generally flexible and resilient rubbers such as natural rubber or rubbers made from conjugated dienes having from 4 to 10 carbon atoms such as synthetic polyisoprene, polybutadiene, styrene-butadiene rubber, and the like, flexible polyurethanes, flexible epoxides, and the like. The cover (80) is secured to an interior wall (7) of the tire. The cover (80) has an adhering surface which secures the monitoring device assembly to a surface of the tire, preferably within the pressurizable tire cavity. As shown in FIG. 7 of the ""065 Patent, the cover (80) may surround the monitoring device assembly (17), and is secured to the interior portion of the tire about the perimeter of the monitoring device assembly. As shown in FIG. 8 of the ""065 Patent, the monitoring device assembly (17) may be located within a tire pocket or recess (75) which can be made by inserting a rectangular billet of appropriate dimensions onto the uncured tire innerliner at the location of the desired recess (75). During tire manufacturing, the curing pressure of the mold will press the billet into the tire inner liner and cure in the recess pocket (75). The cover (80) is then attached about the perimeter of the monitoring device assembly to the tire inner liner. The cover (80) may be co-cured with the green tire or may be attached to the tire after curing by use of various types of adhesives, including ambient temperature amine curable adhesives, heat-curable adhesives, and chemical-curable adhesives such as various self-vulcanizing cements, various chemical vulcanizing fluids, and the like. The flexible cover (80) can be attached to the tire with the monitoring device already in place or, alternatively, the monitoring device, whether or not encapsulated, can be inserted through a slot (84) in a flexible cover (80) which is already attached to the tire. FIGS. 11 and 12 of the ""065 Patent illustrate another method of mounting a monitoring device within a tire. The monitoring device is contained within a housing pocket (90) which has a slot for mounting the assembly within the pocket and through which the antenna (30) of the monitoring device can project after assembly. A band (98) is included for securing and biasing the antenna (30) to a raised portion (102) of the pocket. FIGS. 13 and 14 of the ""065 Patent illustrate a method of embedding the device within a tire, and includes placing the device between a tie-gum ply (199) and inner liner ply (200) of an uncured tire, at a location in the vicinity of the tire crown (202) or at a location near the tire bead (210), respectively. After curing, the device is permanently contained in the tire structure. FIG. 15 of the ""065 Patent illustrates another method of embedding the monitoring device assembly within a tire. The monitoring device assembly (17) is sandwiched between the uncured tire inner liner ply (200) and an inner liner patch (222). After curing, the monitoring device assembly (17) is permanently embedded between the patch (222) and the ply (200).
U.S. Pat. No. 5,731,754 (Lee, Jr., et al.; 1998), incorporated in its entirety by reference herein, discloses a transponder and sensor apparatus (10) for sensing and transmitting vehicle tire parameter data. The apparatus (10) includes a substrate (12) which is preferably flexible. The substrate (12), various sensors, and a transponder (18) mounted on or adjacent to the substrate (12) are disposed in a housing (7) formed of an encapsulating medium. Preferably, the encapsulating medium (7) is formed of cured rubber for compatibility with a vehicle tire, and may be formed to any desired shape. As shown in FIG. 7, the apparatus (10) may be integrally mounted within the tire (60) during the manufacture of the tire (60), and a suitable mounting position is in the upper portion of the side wall (66) adjacent to the bead (64), as this location exhibits the least amount of flexure during use of the tire (60). As shown in FIG. 8, the apparatus (10) may be mounted on the inner liner of the tire (60) adjacent to the bead (64). In this case, the elastomeric patch or membrane (59) is mounted over the apparatus (10) and sealingly joined to the inner liner to fixedly mount the apparatus (10) in registry with the tire. Referring to FIG. 2, another feature illustrated in this patent is an antenna (36).
An electronics package (module) including an RF transponder component of a tire-condition monitoring system may be mounted to an inner surface of a pneumatic tire, either after the tire is manufactured or during its manufacture. This electronics package will hereinafter generally be referred to as a xe2x80x9ctransponder modulexe2x80x9d, or more simply as a xe2x80x9ctransponderxe2x80x9d.
One challenge associated with mounting the transponder (module), is ensuring that the pressure sensor component of the transponder is in fluid communication with the cavity of the tire so that air pressure within the tire can be detected/measured. The aforementioned ""065 Patent (U.S. Pat. No. 5,500,065) proposes various solutions to this problem. FIG. 6 of the aforementioned ""065 patent illustrates, for example, providing an opening or aperture (18) in the encasement or encapsulating material (16) to allow an air path to the pressure sensor (46) so that it can measure the internal air pressure. FIGS. 7 and 8 of the aforementioned ""065 patent illustrate, for example, providing a slit (84) in the cover (80) to allow for detection of air pressure. FIGS. 13 and 14 of the aforementioned ""065 patent illustrate, for example, providing a small removable dowel (206) which will press through the inner liner ply portion (200) of the tire during curing to form a hole or aperture for air passage to the pressure sensor in the monitor assembly (transponder) (17). FIG. 15 of the aforementioned ""065 patent illustrates, for example, inserting a dowel (220) through the inner liner patch (222) and then into the transponder (17). The dowel must be removed after building the tire to allow fluid communication through the hole or aperture to the underlying pressure sensor. This represents an additional step which, if overlooked, can render the transponder inoperative for its intended purpose. Commonly-owned PCT Patent Application No. PCT/US97/22570 discloses using a wicking means associated with the pressure sensor to provide a path for pressure equilibrium between the pressure sensor and the inflation chamber. FIG. 6 of the aforementioned U.S. Pat. No. 5,731,754 discloses a transponder covering which is a thin elastomeric or rubber membrane (59) which transfers pressure from the interior of the tire to the pressure sensor (50) by means of a pressure transfer medium (57) which is disposed in the cavity between the membrane and sensor. Typically, in the mounting techniques of the prior art, the transponder is not readily accessible for replacement or maintenance.
Another challenge when mounting a transponder or a housing (cover) for the transponder (see, e.g., FIG. 10 and the cover 80 of the aforementioned U.S. Pat. No. 5,500,065) during building the tire, is inherent in putting any xe2x80x9cforeign objectxe2x80x9d on the tire building drum during lay-up of the green tire. Such a xe2x80x9clumpxe2x80x9d on an otherwise substantially cylindrical build drum can interfere with (adversely affect) the spacing and/or alignment of cords (wire filaments) laid across (typically in the axial direction) the build drum. These cords are typically on the order of approximately 0.15-0.30 mm in diameter, spaced uniformly, circumferentially about the build drum.
Another challenge when mounting a transponder in a tire during building the tire is inherent in the high levels of heat generally applied during this process. Many electronic components found in the typical transponder are sensitive to such levels of heat, and may be damaged in the process. Alternately, custom-designed and therefore more expensive electronics may need to be selected for use in transponders intended for this kind of use.
An antenna is evidently an important feature of an RF transponder, and specific mention of this feature has been made hereinabove. Generally speaking, there are two main configurations and locations for the antenna of a tire transponder: (i) a xe2x80x9ccoilxe2x80x9d antenna, typically located with the transponder in a package; and (ii) a xe2x80x9cloopxe2x80x9d antenna extending from the transponder about the circumference of the tire.
In addition to these two main configurations and locations, U.S. Pat. No. 4,857,893 (Carroll; 1989), incorporated in its entirety by reference herein, discloses a configuration wherein all electrical circuits of a transponder device, as well as an antenna (receiving/transmitting coil), may be realized on a single monolithic semiconductor chip.
FIGS. 3, 7, 8 and 9 of the aforementioned U.S. Pat. No. 4,067,235 illustrate various configurations and locations of antennas for transponders. As illustrated in FIG. 1, the remote tire pressure sensor (transponder, 21) includes two antennas: (i) a secondary receiving antenna (38); and (ii) a secondary re-transmitting antenna (26). As mentioned above, FIG. 3 illustrates a remote tire pressure sensor (21) encapsulated by a suitable elastomeric compound and bonded to the inner wall of the tire (22). The entire electronic circuit is placed on a semiconductor body or wafer and is surrounded by the secondary receiving antenna (38). Directly below the wafer is the secondary re-transmitting antenna (26). Both antennas (38 and 26) are located within the elastomeric compound encapsulating the remote tire pressure sensor (21). FIG. 8 illustrates an arrangement wherein the secondary receiving antenna (38) is wound around the circumference of the sensor (21xe2x80x3), and the secondary re-transmitting antenna (26) is disposed closely adjacent the semiconductor body (128). FIG. 7 illustrates the secondary receiving antenna (38) extending around and within the periphery of the sensor (21xe2x80x2xe2x80x3), and the secondary re-transmitting antenna (26) disposed closely adjacent the semiconductor body (128). FIG. 9 illustrates a remote tire pressure sensor (21xe2x80x2) in the shape of a sphere which can be introduced inside the tire (22) as a free-rolling element. The sensor (21xe2x80x2) includes a secondary receiving antenna (38) that is circumferentially wound around the surface of the sphere. The secondary re-transmitting antenna (26) is located near the center of the sphere.
FIG. 2 of the aforementioned U.S. Pat. No 5,731,754 illustrates locating the antenna (36) as being a patch antenna mounted on a substrate (12) upon which are also mounted other components of the transponder, such as a battery (14), pressure sensing means (50) and other electronic components (e.g., temperature sensor (110), means (120) for detecting tire revolution, and a timer (134)).
FIG. 11 of the aforementioned U.S. Pat. No. 5,500,065 illustrates an antenna extending from a housing pocket (90) which has a cavity (94) for holding the monitoring device assembly. The pocket (90) also includes a band (98) for securing and biasing an antenna (30) of the monitoring device assembly to a raised portion (102) of the pocket.
The above-described antenna configurations and locations are all examples of small, typically coil antennas which are located with the transponder module itself. There follows a description of a loop-type antenna which extends around the circumference of the tire.
PCT Patent Application No. PCT/US90/01754 (published Oct. 18, 1990 as WO90/12474), incorporated in its entirety by reference herein, discloses a vehicle tire identification system wherein electronic transponders (20) are embedded within vehicle tires (40). The transponder includes a receiver/transmitter coil (26) of one or more loops of wire (54) strategically placed along the sidewall or in proximity to the tread face of the tire. The coil (26) functions as an antenna for the transponder (20) and is coupled to a coil (14) functioning as the antenna of an interrogator (reader/exciter) unit. A typical vehicle tire (40) is shown in FIG. 2. Its inner circumference is reinforced by a bead (41) which is a closed loop of wire. The sensitivity of the transponder antenna/coil (44) is adversely affected if it is too close to the bead (41). Conversely, the tread face (42) of the tire is subject to wear and therefore it is important to locate the coil (44) away from the wear hazard of the tread (42). FIG. 3 illustrates various possible locations for the antenna/coil (44A, 44B, 44C) which is embedded within the carcass of the tire. FIG. 4 illustrates alternative locations for the transponder wires (antenna/coil). For example, at a location (50) which is inside the steel belts but near the inner surface of the tire (45), or at a location (51) which is between layers of steel belts, or at a location (52) which is just outside of the belts and within the tread of the tire. A typical tire transponder is shown in FIG. 5, wherein it can be seen that the transponder antenna/coil (54) is formed of one or more turns of insulated wire or bare wire separated by insulating rubber in the manufacturing process. Acceptable materials for the wire include steel, aluminum, copper or other electrically conducting wire. As disclosed in this patent document, the wire diameter is not generally considered critical for operation as an antenna for a transponder. For durability, stranded steel wire consisting of multiple strands of fine wire is preferred. Other wire options available include ribbon cable, flexible circuits, conductive film, conductive rubber, etc. The type of wire and number of loops in the antenna/coil is a function of the anticipated environment of the tire use and the preferred distance of interrogator communication. It is proposed in this patent document that the greater the number of loops of the transponder coil, the greater the distance of successful interrogation of a given tire transponder.
The aforementioned, commonly-owned U.S. Pat. No. 5,181,975 discloses a pneumatic tire having an integrated circuit transponder which, upon interrogation by an external RF signal, transmits tire identification and/or other data in digitally-coded form. The transponder has a coil antenna of small enclosed area as compared to the area enclosed by an annular tensile member comprising a bead of the tire. The annular tensile member, during transponder interrogation, acts as the primary winding of a transformer. The coil antenna is loosely coupled to the primary winding and is the secondary winding of the transformer. The coil antenna is substantially planar in shape and, when positioned between the inner liner of the tire and its carcass ply, the transponder may include a pressure sensor responsive to tire inflation pressure. See also the aforementioned, commonly-owned U.S. Pat. No. 5,218,861.
U.S. Pat. No. 4,319,220 (Pappas, et al.; 1982), incorporated in its entirety by reference herein, discloses a system for monitoring tire pressure comprising wheel units in the tires and a common receiver. Each wheel unit has an antenna comprising a continuous wire loop embedded in an open annulus which is disposed against the inner periphery of the tire for transmitting signals and for receiving power. The antenna (152) is held against the inner periphery of the tire by its resilience and by centrifugal force. Further, to prevent side-to-side shifting when the vehicle stands still, two or three preferably molded side guides (153) are disposed into the tire. As illustrated in FIGS. 9, 10 and 11, the antenna (152) annulus is formed as an almost complete circle having a gap between its two ends. Wires (155) within the antenna (152) emerge as a pair of output wires (159a, 159b) at a single location from the open annulus. At symmetrical locations about the inside of the antenna, an electromagnetic power generator module, a gas-mass monitoring sensor module, and a signal transmitter are mounted, electrically interconnected, and suitably connected to the antenna wires 159a/159b. The interconnection wires (119a, 119b, 119c, 139a, 139b) are disposed on or in the inner surface of the antenna assembly.
U.S. Pat. No. 5,479,171 (Schuermann; 1995), incorporated in its entirety by reference herein, discloses a long, narrow antenna (14), as illustrated in FIGS. 3, 4a and 4b, mounted to or within the sidewall (30) of a tire. This antenna acts to extend the reading range for the interrogator to be a long range which is generally radially symmetrical about the tire. The antenna (14) comprises a wire which is folded back upon itself and has a coupling coil (16) formed at an end thereof. A transponder (12) has a coil (132) which may be formed as an annulus surrounding other components of the transponder (see FIG. 6) or which may be wound on a small ferrite core (220) (see FIG. 7). The attachment methods described are to affix the antenna (14) and the transponder (12) using an adhesive patch (32), or to use an integrated manufacturing process in which the antenna and transponder might be formed directly within the structure of the sidewall (30) of the tire (20).
It is thus evident that the selection of antenna type and location are non-trivial issues warranting careful design consideration, including issues of how best to connect a given antenna type to a given transponder.
Transponder-Mounting Locations
Other issues relevant to mounting a transponder module in a tire include replacing the entire transponder module if it requires replacement and, in the case of battery-powered (xe2x80x9cactivexe2x80x9d) transponders, replacing the battery if required. Preferably, the transponder, whether xe2x80x9cactivexe2x80x9d or xe2x80x9cpassivexe2x80x9d should represent only a fractional cost of the overall tire. Hence, replacing an entire tire because of an inoperative transponder would be highly undesirable.
In the case, for example, of a transponder unit mounted to the rim, rather than to the tire, such as is shown in the aforementioned U.S. Pat. No. 5,285,189, replacement of the transponder unit would be a relatively straightforward matter of removing the tire from the rim, replacing the transponder unit, and re-installing the tire on the rim.
In contrast thereto, consider the case, for example, of the aforementioned U.S. Pat. No. 4,067,235 wherein (see, e.g., FIG. 3 thereof) the remote tire pressure sensor (21) is encapsulated by a suitable elastomeric compound and is bonded to the wall of the tire (22), replacing the transponder would require de-bonding the elastomeric compound encasing the tire pressure sensor and re-bonding another unit to the wall of the tire. Such procedures require special care and consideration and may, in certain instances, not be feasible without causing damage (however slight) to the tire.
If, as in the aforementioned PCT Patent Application No. PCT/US90/01754 the antenna is an integral element of the tire, embedded in the carcass of the tire, problems would evidently accrue to detaching the transponder from the antenna, and re-connecting a replacement transponder to the embedded antenna -assuming, arguendo, that the transponder itself is not embedded in the carcass of the tire. The patent document describes, for example, how an integrated circuit of an electronic module (55) of a transponder may be mounted on a circuit board or substrate providing for attachment of the transponder antenna/coil wires (54) by any suitable means including welding, soldering, bonding or suitable cement.
In the case of permanently embedding the transponder within the tire, such as is shown at FIG. 13 of the aforementioned U.S. Pat. No. 5,500,065, replacing the transponder unit or any component thereof is a virtual impossibility.
The aforementioned, commonly-owned U.S. Pat. No. 5,181,975 discloses a number of locations and techniques for mounting a transponder (24) within a tire. In a tire that has already been manufactured, the transponder (24) may be attached to the axially inner side of the inner liner (30) or to the axially outer side of the tire sidewall (44) by means of a tire patch or similar material or device. (see, e.g., column 11, lines 61-65). Commonly-owned U.S. Pat. No. 5,218,861 also discloses locations and techniques for mounting an integrated circuit transponder and pressure transducer within a pneumatic tire.
A final design challenge, whether or not recognized as such by the prior art, is to provide a single, or readily modified method and apparatus for mounting a variety of transponders within a variety of pneumatic tires, with as much commonality between the variations as is possible.
It is an object of the present invention to provide method and apparatus for mounting an electronic device such as a transponder module and an antenna in a pneumatic tire, as defined in one or more of the appended claims and, as such, having the capability of being implemented in a manner to accomplish one or more of the subsidiary objects.
It is another object to provide method and apparatus for mounting a transponder module in a pneumatic tire in a manner such that the transponder may conveniently be inserted, removed, replaced and/or maintained, either during tire manufacture or after, and such that a sensor associated with the transponder is exposed to conditions within the tire.
It is another object of the present invention to provide method and apparatus for mounting a transponder and an antenna for the transponder within a pneumatic tire, and to provide for effective transformer-type coupling between the transponder and the antenna.
It is another object of the invention to provide a method for mounting a transponder module in a pneumatic tire at any point in the tire manufacturing process, with minimal impact on tire performance.
According to the invention, a patch for mounting a transponder module to an inner surface of a pneumatic tire has a body formed of a resilient material. An opening extends an external surface of the patch to a cavity. The cavity is sized and shaped to be approximately the same size and shape as the transponder module. The patch is preferably formed of a resilient material, such as halobutyl rubber. The opening preferably has a smaller dimension than the cavity, thereby forming a resilient lip about the opening, the lip being sized somewhat smaller in a corresponding dimension than the transponder module so that the transponder module may be inserted through the opening into the cavity by deflecting the lip and thereafter retained within the cavity by the annular lip. In an embodiment of the invention, the opening is circular and the lip is annular. At least one slot may be provided on the lip to facilitate deflecting the lip for inserting the transponder module past the lip into the cavity.
According to a feature of the invention, a coupling coil comprising at least a few turns of wire is disposed within the body of the patch, closely adjacent the cavity. The coupling coil is preferably concentric with the circumference of the cavity, and may either surround that circumference or be positioned close below it (on the side of the cavity opposite its opening). The coupling coil may be formed integrally with the patch, during a molding process, or may be disposed around or within a bobbin which is molded into the body of the patch.
According to a feature of the invention, an antenna is provided, having two end portions, each of which are electrically connected to a respective end of the coupling coil. The antenna extends circumferentially about an inner surface of the tire.
In an alternate embodiment of the invention, contact pads or plugs are provided in the patch, and the antenna is electrically connected to these pads/plugs. In this manner, a transponder module having contact pads on an external surface thereof may be electrically connected to the antenna when the transponder module is disposed within the cavity.
According to an aspect of the invention, the antenna may be a wire which is embedded in one or more elongate rubber strips which are disposed circumferentially about an inner surface of the tire. The wire may be an elongate helix, or a single elongate strand of wire, or multiple strands of wire, or braided wire. Alternatively, the wire may, in essence, be a conductive pathway formed of a material selected from the group consisting of carbon containing material, carbon fiber, carbon black and particulate graphite. These rubber antenna strips may be integrally molded with the patch.
According to a feature of the invention, end portions of the strips of rubber within which the antenna wires are embedded are of a conductive rubber composition. In this manner, when these end portions are overlapped, a complete 360 degree loop antenna may be formed on an inside circumferential surface of the tire.
According to alternate embodiments, antenna wires emanating from the patch as described hereinabove may be disposed circumferentially about the inner surface of the tire without electrically connecting the outer ends, thus forming a dipole antenna, instead of a loop antenna.
Other objects, features and advantages of the invention will become apparent from the description that follows.